By MATT FLEGENHEIMER

April 1, 2013

There were perhaps a few hundred feet of unity in Grand Central Terminal on Monday, stretching from the subway entrance on East 42nd Street and Park Avenue to the trains bound for competing boroughs.

The fans arrived to greet the same baseball season, gabbing with the same unblemished optimism. Some even shared a fashion strategy — pulling a team T-shirt over a work-approved button-down, once the boss was out of view.

But in a two-team baseball town, on an Opening Day without precedent in the last half-century, the split took place. On the No. 4 train platform, Yankees fans boarded their ride due north, for a date with the Boston Red Sox. And one level below, beneath the pinstriped faithful — in a cruel bit of transit symbolism not lost on the city’s Mets fans — the No. 7 train to Queens awaited.

Play ball! About 10 miles apart.

Because of a scheduling oddity, the Yankees and Mets both began their seasons at home, on the same day, at the same hour, for the first in their history, according to the Elias Sports Bureau.

Though the quirk had little effect on the most loyal fans, it introduced a unique logistical wrinkle for many others — ticket scalpers, transit officials, bartenders holding television remote controls, even Mayor Michael R. Bloomberg.

And so, on a day typically governed by the teams’ off-season choices — Who plays shortstop? Where does he hit in the order? What’s the going rate for a pretzel? — the most critical question was turned on the city itself before the games’ first pitches were thrown shortly after 1 p.m.

Yankees or Mets?

Mr. Bloomberg took care to appear evenhanded. His chief spokesman, Marc La Vorgna, wrote on Twitter before the games that “heavy calculations” were made to ensure that the mayor split his time equitably. These included research on the average game length for each team, specifically for the Yankees and Red Sox, whose marathon meetings are without peer. (The mayor took the subway to the Yankees game first, stayed until the fourth inning, then arrived by car at Citi Field for the sixth inning, Mr. La Vorgna said. He stayed until the end.)

At a Modell’s on East 42nd Street, employees likewise arranged team apparel with an eye toward fairness, placing Mets and Yankees gear side by side near the entrance, though some of the Mets racks were banished to a well-obscured corner.

Bar operators turned to the democratic process in determining which game to display most prominently. At Shorty’s, a bar in Midtown known as a haven for Philadelphia sports fans, the bartender, Catherine Tejada, said that all but two tables requested audio and big-screen treatment for the Yankees. (One wanted the Mets; the last asked for the Colorado Rockies.)

A scheduling oddity had the Mets and Yankees both begin their seasons at home, on the same day, at the same hour. A fan at Citi Field showed loyalty to both teams.

Karsten Moran for The New York Times

Yankees fans also had their way in other corners of the city. The Metropolitan Transportation Authority provided a special nostalgia train to the Bronx, with cars from 1917 and nonstop service to the Stadium. The Mets received no such accommodations.

“We don’t have the personnel to be able to run two nostalgia trains at once,” said Kevin Ortiz, an authority spokesman.

He added that an old train would likely to run to Citi Field for this year’s All-Star Game and “hopefully to both stadiums come October.”

Stephen Rozenfeld, 79, from New Rochelle, N.Y., is used to such slights. Wearing a shirt with the name and number of the Mets third baseman, David Wright, atop his collared button-down, Mr. Rozenfeld said he had cheered the team since its inception in 1962.

“I call being a Mets fan the logical masochistic extension of being a Dodgers fan,” he said, signaling the start of a lengthy soliloquy on the Brooklyn Dodgers’ 1941 loss to the Yankees in the World Series. “Suffering is part of the game.”

Outside the ballparks, it was clear which game the city’s hucksters preferred. In the Bronx, ticket scalpers held court beside a McDonald’s, lamenting that they could not work both games this year. Customer loyalty, some said, had tethered them to the Yankees. “I’ve worked here longer,” one scalper reasoned, “so I’ve got be here.”

Nearby, a dog named Shaggy sat atop a security pillar in a Yankees hat, sunglasses and Converse sneakers. Tip money stuck out of the back left pocket of the dog’s denim jeans, though it would be scooped up soon enough by Ryan Legrier, 27, who had turned his Maltese-poodle mix into a small business.

By afternoon’s end, though, Citi Field would prove the place to be. Hours earlier, as the scent of lighter fluid wafted over the parking lot’s tailgaters before the first pitch, Jason Kish, 37, had blessed Opening Day’s promise of a “fresh start.”

He had attended about 20 season openers, he said, as a co-worker, John Keskin, a Turkish native, awaited his first. “Mets, baby!” Mr. Keskin shouted, tilting his head to the sky.

Soon, their faith was rewarded. The Mets routed the San Diego Padres, 11-2. And all the ancient trains and bespectacled pooches in the five boroughs could not have saved the Yankees from an 8-2 loss.